The present invention relates to a drive system for a closure member configured to selectively close an opening of a vehicle roof, and in particular to an automotive sunroof system.
In a typical automotive sunroof system, a pair of side frames each fitted with a guide rail extend in a fore-and-aft direction on either side of a roof opening. Each side frame has a front end adjacent to a front edge of the roof opening and a rear end extending further rearward from a rear edge of the roof opening. A pair of sliders supporting a slide panel are slidably supported by the corresponding guide rails, and to each slider is connected an end of a Bowden or push-pull cable which is configured to be pushed and pulled as required by an electric motor located centrally in a front frame extending along the front edge of the roof opening. Thereby, the slide panel can be moved in a fore-and-aft direction between a closed position fully closing the roof opening and an open position fully exposing the roof opening.
The push-pull cable typically comprises an inner wire including a steel core wire and an additional outer wire wrapped spirally around the core wire, and, optionally, a sheath pipe or a housing that slidably receives the inner wire. The push-pull cable is normally held in position to the corresponding side frame by using cable guides integrally formed in the side frame, and extends substantially linearly along the length of the side frame. A relatively rigid drive pipe made of steel extends from the front end of each side from to a drive gear of the electric motor, and an idle pipe extends from the drive gear away from the drive pipe so that the section of the push-pull cable extending from the front end of the side panel past the drive gear of the electric motor may be guided without any significant deflection in spite of the significant tension and compression that is required to be transmitted by the push-pull cable.
Such a drive pipe and idle pipe are required to be bent in a complex configuration, and this contributed to an increase in the cost of the sunroof system. Japanese patent No. 3043589 (patent document 1) discloses an automotive sunroof system including a pair of drive pipes that are disposed on a common plane and a pair of idle pipes that are made of relatively flexible plastic material. Thereby, the work required for bending the drive pipes can be simplified, and the generation of noises due to the collision between the drive pipes and idle pipes that can be caused by the vibrations of the vehicle can be avoided.
Japanese patent No. 3994815 (patent document 2) discloses an automotive sunroof system in which a front frame made of plastic material is integrally molded with guide pipe portions for receiving the push-pull cable therein. This prior invention allows the number of component parts to be reduced.
According to the invention disclosed in patent document 1, the drive pipes are made of steel, and the need for bending steel pipes prevents the reduction in the manufacturing cost and weight. Because each drive pipe is required to protrude ahead of the front frame for the purpose of avoiding a sharp bending of the drive pipe, the protruding parts of the drive pipes are prone to inadvertent deformation during the handling of the sunroof assembly, and any deformation of the drive pipes may ruin the whole drive system of a sunroof system.
In the case of the sunroof system disclosed in patent document 2, the number of component parts can be reduced owing to the elimination of the drive pipes, but a highly complex die assembly is required for molding the front frame, and this increases the manufacturing cost. Furthermore, because the guide pipe portions cannot be molded so as to entirely surround the push-pull cables, a measure is required to prevent grease from dripping from the guide pipe portions. It is also difficult to entirely eliminate noises that are caused by the sliding contact between the cable and guide pipe portions.
The guide pipe portions are typically given with a highly complex configuration, and this tends to cause poor dimensional and geometrical precision. If there are burrs in the guide pipe portions, the sliding engagement between the burrs and cables cause noises.